Retrofitting Torsen diff

fshol said:

Thanks for the answer. I do mean the complete assembly, which means that i don't have to worry on adjustments etc. Beside changing the assembly, i guess you will only have to remove and reinstall the driveshafts, which should not be too difficult? Since we don't have too many Raptors over here, I will probably have to buy a complete new assembly

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Yeah, to swap a complete assembly isn't a difficult job. Like you said, drive shaft, cv shafts, a few mounting bolts..

pirate air said:

Yeah, to swap a complete assembly isn't a difficult job. Like you said, drive shaft, cv shafts, a few mounting bolts..

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I am assuming the front suspension has to come apart to get the CVs out, is that right?

KaiserM715 said:

I am assuming the front suspension has to come apart to get the CVs out, is that right?

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Yeah, partially. Upper ball joints and outer tie rod ends come loose. That should give you enough play to pull the inner axle snub shafts from the diff housing.

This came up in conversation over the weekend. There is 'talk' that there might be some trouble in paradise for Torsen/Raptor owners. And those of us considering retrofitting might/probably run into the same issues.

Apparently, Ford is seeing a disproportionate number of warranty claims on 2012+ Raptors with the Torsen diff; the CV axles are failing. From what I understand, the axles are the same as what all Raptors have; they were not upgraded in any way to handle the added stresses or strains. And, apparently, they're starting to fail in the field as a result.

There's something called a "safety factor" when it comes to parts like these. A safety factor of 1, for example, means that the part is exactly as strong as it needs to be, to handle a load exactly equal to the max its ever expected to handle. So if PartA is designed to handle 100lbs of weight with a safety factor of 1, that part will (in theory) fail when 101lbs is applied. If it had a safety factor of 1.5, that means it will not fail until 151lbs is applied and so forth.

I've learned that a "good rule of thumb" when it comes to axle strength and safety factors is this:
-for an open diff, the part should have a safety factor of 2.
-for a limited slip diff (like the Torsen), the safety factor should be 5.
-for a fully locking diff, the safety factory should be 10.

Again those are just general ball park numbers that serve to give an idea where the relative strengths probably ought to be. If that rule is accurate and true, its no wonder Ford is seeing the Torsen equipped 2012s+ fail.

This has put any thoughts of retrofitting on hold for me. I am going to wait and see what the aftermarket does in terms of upgraded cv axles before reconsidering.

FWIW and YMMV.

Just wait till after the Texas run and see how many 2012 have issues...

-Greg

BigJ said:

Apparently, Ford is seeing a disproportionate number of warranty claims on 2012+ Raptors with the Torsen diff; the CV axles are failing.

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Do you know of any specifics as to which part of the CV shafts are failing?

I know there are a couple of companies that make upgraded CVs using upgraded materials (usually 300M or similar). I am not aware of anything like that out there for our application.

Here is an example for the G8:
300m Axles for the G8
Here is the company (they specialize in GM):
GFORCE ENGINEERING, LLC

As a note, these axle upgrades run about $1500 and up (relatively custom and low volume). Find another, stronger application to adapt, the cost comes down.

BigJ said:

There's something called a "safety factor" when it comes to parts like these. A safety factor of 1, for example, means that the part is exactly as strong as it needs to be, to handle a load exactly equal to the max its ever expected to handle. So if PartA is designed to handle 100lbs of weight with a safety factor of 1, that part will (in theory) fail when 101lbs is applied. If it had a safety factor of 1.5, that means it will not fail until 151lbs is applied and so forth.

I've learned that a "good rule of thumb" when it comes to axle strength and safety factors is this:
-for an open diff, the part should have a safety factor of 2.
-for a limited slip diff (like the Torsen), the safety factor should be 5.
-for a fully locking diff, the safety factor should be 10.

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I wouldn't look at it as a different safety factor. The difference is that the limit load increases as you become "more locked". The safety factor would very likely be the same for all three cases.
Following J's thinking using example numbers:
Open limit load = 1000 ft-lbs; with safety factor (2) = 2000 ft-lbs design limit / component capability
Torsen limit load = 2500 ft-lbs; with safety factor (2) = 5000 ft-lbs design limit / component capability
Locked limit load = 5000 ft-lbs; with safety factor (2) = 10000 ft-lbs design limit / component capability

Using this example, the limit load for the Torsen is already 500 ft-lbs over the design limit (limit load + safety factor) for the stock shafts.
NOTE: These are made up numbers, DO NOT take them to the bank.

For further discussion, safety factors for aerospace are 1.0 for yielding (metal twists, stretches, bends - what we would consider broken) and 1.4 ultimate (metal has ruptured, broken into multiple pieces). For construction equipment (backhoes, dozers, etc.), they use 1.15 FSy and 1.5 FSu (for one manufacturer that I am aware of). I would suspect that automotive would be similar to that. As the factor of safety goes up, so does weight, size and cost.

Keep in mind that in first gear, low range you are looking at a 45:1 torque multiplication of a 430 ish ft-lb engine.

Hey guys, I am currently work on a complete new front end for my truck. I spent a lot of time comparing the Various LSD's, and have decided to work with Wavetrac. Wavetrac® Differential - A torque biasing differential with a difference

They are having to engineer a reverse cut setup for us, but we are already working on it.

I am also working with RCV to upgrade the axles and hubs to handle the added stress these systems throw on the driveline.

I will keep you up to date as we engineer this and get it working.

Should be fun.

Chrisandalex1 said:

Hey guys, I am currently work on a complete new front end for my truck. I spent a lot of time comparing the Various LSD's, and have decided to work with Wavetrac. Wavetrac® Differential - A torque biasing differential with a difference

They are having to engineer a reverse cut setup for us, but we are already working on it.

I am also working with RCV to upgrade the axles and hubs to handle the added stress these systems throw on the driveline.

I will keep you up to date as we engineer this and get it working.

Should be fun.

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Awsome... RCV are great! I believe this is a needed upgrade for the Raptor!

-Greg

If the shafts are upgraded, I wonder where the next weak link is? I know I have heard of a couple of busted axle housings....

KaiserM715 said:

If the shafts are upgraded, I wonder where the next weak link is? I know I have heard of a couple of busted axle housings....

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The Blue oval!

-Greg